text:
radius detail of corner of stub beam web
existing repair on stub beams beneath the passenger cabin floor is characterized as following:
"The existing repair must have removed the radius detail of the lower
inboard corner of the stub beam web"
Do you have any idea on what "radius detail" means?

This has nothing to do with Aviation, as defined in the Help Center.

this is about internal structure of 737-300

General terminology about structures, even structures used in an aircraft, is off topic, just as questions about food, even food prepared & served on an aircraft, would be off-topic.


text:
Thoughts on Idea - AP Disengage, Land Flap Selection
When AP disengages the aircraft goes into a slight roll or the possibility exists for the aircraft to go into a degree of roll.
Do you think it would be prudent for airlines to include as an SOP for Land flaps to be selected before AP disengages on final approach to minimize the pilot work load while manual flying? - This is viewing the situation from a safety perspective on an aircraft like 787.
I am new to the aviation business.

Which aircraft? What AP mode? What circumstances?

Say a 787, on approach. AP disengaged.

@oshsec [edit] your question to include that info up there. Not everyone will read the comments.

I think more important is having auto trim after disengage.

Until 2013 several airlines promoted the idea of using as much automation as possible during all phases of flight to improve safety. The idea was that autopilots are less likely to make handling mistakes than human pilots and the pilots can focus on other tasks, especially during high workload situations.
However, the FAA noticed a decline in pilots hand-flying abilities and eventually published SAFO 13002:

A recent analysis of flight operations data [...] identified an increase in manual handling errors. [...]
However,
continuous use of autoflight systems could lead to degradation of the pilot’s ability to quickly recover the
aircraft from an undesired state. [...]
Operational policies
should be developed or reviewed to ensure there are appropriate opportunities for pilots to exercise
manual flying skills [...]

It is generally better if pilots regularly experience how the aircraft feels and responds by hand-flying it. This includes feeling how the aircraft responds to changes in the flap position. Never experiencing this in the real aircraft reduces the pilot's ability to hand fly when it is needed (e.g. autopilot not operational).

Thank you for the feedback. Learning a lot in this business.

Unfortunately, there's nothing that will enforce this for Joe Average car driver who has a self-driving car. Eventually, the self-driving computer will say, "tap-out, it's on you now", and I've seen instances of drivers who are otherwise engaged while the magic of tech does the driving - they have zero situational awareness and will end up as dangerous as a new driver during his first driving lesson because they'll be so out of practice. Of course, this could be remedied by a semi-annual driving test, but that'll never happen in the US. :(

That's an interesting comment FreeMan. Data monitoring programs to overlook operational safety of these systems is my initial thought on combatting the risks.

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V-22 aerial refueling
Boeing worked on an aerial refueling pod for the V-22 that can both refuel other aircraft in air and be offloaded to provide fuel to land vehicles. That seems like a no brainer for the British to purchase as well as any other navy that doesn't have on-ship tankers like the F/A-18 or upcoming Stingray tanker as well as a great addition to disaster relief efforts.
Why has there been no progress for years on that project?
https://news.usni.org/2015/07/29/davis-v-22-aerial-refueling-system-should-be-ready-for-early-f-35-operations-despite-1-year-delay
https://boeing.mediaroom.com/Bell-Boeing-V-22-Osprey-Deploys-Refueling-Equipment-in-Flight-Test

Would be good to add some links to which Boeing system you are referring, since this is an active area of with various projects, submissions and actual products around. Short answer would be that governments try not to spend ALL the tax payer money on shiney stuff, so there will always be cool things left on the shelf.

It is in production, in use, and is called VARS (V-22 Aerial Refueling System).
V-22 Refueling Contract Highlights Close Ties To F-35

That would be great if it's true, but as far as I can find on the internet it's not. There are lots of articles from 2016, 2018 saying they're moving forward with it, but  none that I can find saying that it's actually up & running and deployed.

The Navy did not, the Marines did.

@JuanJimenez Is there anything more recent than 2016 that discusses that the Marines did get this deployed?  (I've cleaned up the rude comment, but it's a fair point to be seeking something for recent than 2016.) Thanks

I have not searched for anything more recent. Google is available to everyone.

I've done a research and while there are newer articles for example (https://nationalinterest.org/blog/buzz/aerial-refueling-brings-v-22-osprey-whole-new-level-198974) they all seem to refer back to the same 2018 Marine Aviation Plan.

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Can my plane get off the ground?
I'm building a ultralight aircraft. I have a Rotax 447 that produces 40 horsepower and 175 pounds of thrust. The plane is going to have a wingspan of 20 feet by 5 feet and the max takeoff weight of my plane will be 400 pounds including me. It produces 480 pounds of lift including the drag. Mind you I will get professional advice but this is just some advice. Can it get off the ground? What propeller should I use?

What do you mean it produces 480 lbs of lift? At what airspeed/angle of attack?

480 pounds of lift at 24 knots (the maximum stall speed) and 10 degrees

If you don't know what prop you're using, how do you know the thrust this might produce?

That's just the most efficient way it will probably be a smaller amount

Just look at similar design to have an idea: the Pterodactyl has more or less the same weight and needs only 16hp

Ok thanks! I'll look into it

No, you should assume that your craft will not leave the ground.
Not because of any specific performance value, but because you're building from scratch an aircraft that can very easily kill you if even one out of a whole host of details isn't correct, and you're asking an Internet forum questions like "what propeller should I use" and "can this get off the ground?"
Until you have a design that was drafted by a professional, with all such questions answered well before the first step of construction starts, you absolutely should not plan to entrust your life to this craft and any answers you get here.
The level of assurance that "I think this might work" is fine for foam and balsa wood gliders, but you need far more certainty than that before any person goes flying, or attempts to, in such a craft.  The early history of aviation has plenty of examples of craft that flew, barely, just high enough to produce a fatal crash when something went wrong.
Planning to be flying at your stall speed isn't a very good plan; until you know (with far better assurance than random people on the internet can provide) that your craft can fly with adequate margin above stall speed, at reasonable bank angles, while climbing or encountering gusts, you have no business allowing anybody, including yourself, to take it flying.
No, this should never get off the ground!

I'm not going to be flying at stall speed that's just the speed I need to get off the ground and I'm using sticka spruce and I'm going to get it checked by the faa


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How can a non-pilot land a single-engine plane in an emergency?
Can a non-pilot land a single-engine plane in an emergency? Not a big plane with hundreds of passengers and lots of computer stuff, I mean a little plane (light aircraft, propeller up front, just a few passengers).
I sometimes travel to remote areas that are only accessible by single-engine airplane (for photo-safaris and such). The planes are usually big enough for maybe 6 - 20 passengers, and rarely have a co-pilot.
On one trip a few years ago, the day after I arrived at camp, a couple arrived and told us their pilot had gotten sick mid-flight. Everything was fine, he just had a stomach bug and he recovered and landed safely and then flew back to town. But I've always wondered what would have happened if he had passed out or something.
Is it possible for a non-pilot to somehow manage to land the plane? Assuming the pilot passes out and someone jumps into the copilot seat quickly, and picks up a headset and starts frantically calling for help. Can someone on the ground coach them through a (probably crappy) landing?
For some background, most of the time I've been on these sorts of planes, they're landing on a dirt airstrip with a wind-sock and some safari guides who have chased away any animals that may have been on the airstrip. There's no refueling out there, so the planes must always have at least enough fuel for a round-trip, so theoretically you could turn around and do your crappy landing in town, which would be better equipped for emergencies.
Here are some pics I've taken over the years of the cockpits.. I can barely tell them apart lol. I've sat in the co-pilot seat a few times when seating was limited but I honestly never paid all that much attention to what switches were being flipped during takeoff and landing..
edit: Note that in my particular scenario, these flights are always during the day, so visibility should not be an issue.

Sometimes the passenger/pilot is unnecessary https://en.wikipedia.org/wiki/Cornfield_Bomber

It all depends on the weather and the time of day or night.
Daytime VMC - that is, when you can see the terrain clearly?
Point the plane at some smooth terrain and slowly reduce power; bring it back up a bit if the plane starts sinking or the airspeed needle is about to exit the green area. This is oversimplified, but will usually get you down in one piece; most people get it their first time in a sim.
Nighttime VMC or over water? Call for help and look for lights.
The linked questions contain some instructions. Navigation help will be important.
IMC - that is, when you can't see anything outside?
Establish radio contact for some chance to be talked down to a landing, or pray to your deity. Instrument flight is challenging, non-intuitive, and responsible for a lot of accidents.
If this is a practical concern, some knowledge and practice can be very useful. Knowing your plane's approach and stall speeds and practicing a few glideslopes in X-plane can go a long way.

Thanks @Therac, so to expand a bit - let's say I'm slowly reducing power (moving the throttle lever) and the plane is losing altitude. Ok great.. what do I do when the wheels touch down? Cut throttle entirely? Hit some sort of a button for brakes? Open the door and jump out, hoping I'm good at rolling? I forgot to mention that these flights are always during the day, they don't fly at night because the landing strips aren't lit up (among other reasons). I'll update the question with that info!

@MikeWillis For practical use, of course get more information than that - read the plane's manual, ask the pilot, and practice in a simulator! But basically, you'd cut the throttle and push the pedals with your toes to brake.

"Instrument flight is challenging" – That's a bit of an understatement. I've heard stories of experienced VMC pilots who flew into IMC with an instructor for the first time, and it took all but thirty seconds for them to get turned upside down hurtling to the ground while swearing they were straight and level.

TBH, I wouldn't be surprised if operating the radio was the hardest part.

"the needle crawls to the edge of the green" What does this mean, especially for a non-pilot?

@FreeMan That airspeed stays in the green zone. I admit I was a bit flippant, it takes quite a bit more than one SE answer to learn to land a plane properly. Flaps, toe brakes, power cutoff. But the simple maxim of "descent with your throttle, but don't stall" is a start.

Most people, if thrust into this situation, won't even have the benefit of one SE answer to assist them.

Yes, non-pilots have successfully landed small aircraft many times. Unfortunately not every time. If you would like to be better prepared then the average passenger, get a copy of MS Flight simulator for under a $100 bucks and teach yourself to fly and land a small plane. It is not that difficult when everything is going well. It will also improve your enjoyment on such flights because you will know what the pilot is doing and why. If your pockets are a bit deeper, you can go and get a couple of introductory lessons. It really is great fun, and if the need ever arises, you would be a lot more confident having someone talk you down over the radio.

Yes. Non pilots can and have land small aircrafts. Their was such an incident reported by CNN on May 11th, 2022 where a single-engine Cessna 208 was landed by the passengers after the pilot went incoherent mid-flight. Luckily, a off-duty air traffic controller and certified flight instructor was on the scene and able to instruct the pilot on how to land the plane.CNN news article here

Coincidentally, it seems that the pictures in the question were also of a Cessna 208 Caravan.


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Do the polar curves have large differences in takeoff than in landing?
I was wondering if the polar curve has differences in the takeoff due to the smaller extension of the flaps (this is half that in the landing) that changes the AOA for $ C_ {la} = 0 $. In addition, should I calculate the landing polar on approach?

Yes, in most cases. How large? That depends.
A classic simple flap does these things to lift:

Adds an approximately constant amount of lift at a given AoA in the linear range. For small flaps deflections $\delta_f$ (up to about 15°, typical for takeoff), this amount is proportional to the deflection. After that, flow separates from the flap, and the lift return per deflection diminishes, down to zero in some cases.

For real wings of finite span, the added lift will depend on AoA itself, causing slight reduction of $C_{L\alpha}$. However, if we start considering real flaps that occupy only part of the span, situation will get more complicated; in some cases characteristics may improve with small deflections due to better lift distribution.

Loss of lift at stall becomes more abrupt, often much more.

This can be illustrated by this example from Hoerner, Fluid-Dynamic Lift, Chapter V:

Fowler flaps will increase the $C_{L\alpha}$ derivative.
However, this by itself does not show much how the polar changes, apart from the distribution of $\alpha$ along it. We need to know how drag changes as well. As it happens, there is more added drag than lift, often dramatically:

Source: ibid.
Thus, overall and typically, the polar will shift up and right, more to the right than up. The polar coefficient (how much the curve 'slopes' to the right proportionally to the square of lift) may change either way, but usually not by much.
However, note that flaps are not the only difference between takeoff and landing. For propeller-driven aircraft, propwash will affect the polar significantly, and obviously more so on takeoff than on landing. In this question there is an example of such polar.

The $C_L(\alpha)$ curve changes with flap/slat extension, so it should logically follow that the polar will also change, since the induced drag depends on the lift.
Furthermore the parasite drag will most likely change as well due to a changing airfoil surface.
So yes, the polar needs to be recalculated for all flight configurations.

This should be accepted as the correct answer.

@jimmy i was actually going to add a few images to illustrate now that the bot bumped this.


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How are forces on the landing gear reduced or compensated for at touchdown?
When an aircraft lands with the tires of the landing gear at rest, as soon as the the aircraft touches down, the landing gear experiences a large amount of wheel-spin up forces (because of the static friction involved between the stationary tires and the relatively moving runway at a very fast speed), which even cause it to vibrate at some frequency. This force is considered to be highly undesirable.
Are airplane manufacturers using any kind of measures to reduce these forces on the landing gear at touchdown? How are they compensated?

Edited to remove ambiguity. Thanx for pointing out.

There is a thread on motor-driven gear wheels around, but I can´t find it right away.

My friend is working on motor driven gear wheels, which causes significant reduction in loads on the landing gear while touchdown. But I was curious to know if this has been implemented already

http://aviation.stackexchange.com/questions/9101/does-it-make-sense-towing-airplanes-to-the-head-of-airstrip-by-external-means/9103#9103
Found it..!! But its being tested only for taxiing

Nice - I guess your question differs quite a bit with regard to the motivation for such a thing. Let´s see if someone can contribute...

Which forces do you mean?  There are forces in all 3 axis.  The longitudinal forces caused by stationary tyres hitting the runway exist only for a brief moment when deceleration forces take over.  Do you mean the Z axis?

I am talking about the forces acting parallel to the velocity of the aircraft.

Related topic: http://aviation.stackexchange.com/questions/3702/why-are-aircraft-tires-not-pre-spun-prior-to-landing-to-preserve-them/3705#3705

In its current form, this seems to be almost an exact dupe of the link posted by ROIMaison.

Moving tire and stationary runway results in static friction??

There are lots of forces acting on the gear at the point of landing. The best way to minimize loads on the gear is to land smooth (I know that sounds obvious).
For what it's worth you do not necessarily want to spin up the gear before landing for a few reasons. First off you would need to spin up the gear to precisely (or at least very close to) the speed that the plane was going to touch down at. If you spin the gear up faster you actually will create a problem by accelerating the plane when it touches down. Spinning the gear up can also have a serious gyroscopic effect (since you now have a fast rotating mass) (see here as well) that will affect the handling of the aircraft.
On top of that remember that in aviation it's often about cost. What are the costs to maintain a system that pre-spins the gear vs the cost of tires. Some times its actually cheaper and easier to make a part that wears out some what quickly and replace it often, then design a complex system that require maintenance and up keep.
It appears that some devices for spin up have been looked into but the rotational inertia problem seems to be more of a concern than wheel wear. I would imagine that unintentional side loads on gear are a bigger issue and bigger cause of wear on the landing assembly. Keep in mind that the addition of an assembly like this also adds weight to the aircraft, and no one likes weight that is not needed.
This is a great research paper on the topic that suggests (in their conclusion) a pre spin situation would see 1.07% of the wear of a static situation. They go on to state that that they used a simple linear approximation and only accounted for forces in one direction but it would seem that it is beneficial for the tire.
On a side note this article even suggests the tires can be remolded so even if the are replaced often it seems they are recycled a few times.

an A340 will complete roughly 6,000 take-offs and landings, calling for about 25 sets of replacement tires, each 1.30 m high and weighing about 200 kg. The tires can be remolded several times before they are finally scrapped.

In general, it's the job of the pilot to reduce the forces on the landing gear when landing. One of the best descriptions I have ever heard of landing is that the goal is not to land but to "transition". In other words what you really want to do is transition the load from the wings to the landing gear as smooth as possible, this will reduce the load on the gear. In some cases (short runway heavy plane) your landing may see more force on the gear. I have never flown a 737, but I can tell you that I can put a Piper Warrior down on a 7000-foot strip with out ever feeling that you have touched the ground.

... aka a "greased landing" or "greaser". The primary maneuver used to "transition" from the glide slope to touchdown is called a "flare", and it can be done with a slight pitch-up, a little more engine power, or both, the idea being to curve your flight path upward from the glide slope to level flight, just as your wheels touch, then power to idle, set the nose gear down, thrust reversers or reverse prop pitch (if equipped) coupled with wheel brakes to slow to taxi speeds, retract all control surfaces, and clear the runway. Easy.

Comprehensive, but the paragraphs that relate to tire-maintenance and pilotage are a bit side-topic. The question is more focused on the design of airplanes, which can be expanded in this answer a bit more.

Claiming that you'd need to spin the wheels up to exactly the right speed is an example of the nirvana fallacy: you're rejecting a potential improvement because it doesn't completely eliminate the problem it tries to solve. The acceleration to the plane from hitting the ground with tyres rotating too fast would be negligible. Spinning the wheels at anything greater than zero and less than twice the correct speed would decrease tyre wear from skidding. So we must (and you do!) look for other reasons to reject the idea.

The second part of the question is simpler. Aircraft are designed to handle all operational loads (=limit loads) as defined in the FAR or other regulations. Plus they have reserve strength requirements for larger loads (1.5 times or 1.25 times the limit loads). This latter loads are the ultimate loads, which the aircraft are usually required to stay-together for about 3 seconds.
Reducing wheel spin-up forces is desired, but it is not a winner of the trade-off against the complexity that arises from adding additional systems to spin the wheels up, before touchdown. It takes tremendous efforts to add new functions to existing, proven systems (landing gears in this case), and to prove that they will not fail under normal and foreseen failure conditions. If they will fail, then the structure will neglect the existence of such systems and the benefits of reducing loads would be gone.

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How is Maximum Take Off Weight determined?
How would a test pilot determine the MTOW of an aircraft. Does the manufacturer predict this value?

how about asking for "flight tests that result in updating the MTOW" or "flight tests that are conducted to determine the MTOW". The test pilot does not determine the MTOW limitation himself/herself, they do what the test procedure asks for.

Just as a matter of information, determining the MTOW can involve things you might not normally think, especially on some aircraft. For example, the MTOW of some B747-400BCFs depends in part on both the fuel density and the CG. If the fuel density is 6.43 to 7.1 lbs/gal, you're allowed the full 870000 lbs (assuming an adequate runway of course). If the density is 6.0, the MTOW is 820000. Between 6.0 and 6.43, it varies depending on the CG. Those numbers are from section 1-05-001 of http://terryliittschwager.com/WB/manuals/747-400BCF_GPR1_WBM10.pdf.

Pilots do not determine the official MTOW of an aircraft. MTOW will be estimated by the manufacturer during the design of the aircraft based on the required payload of the aircraft and the design configuration. It will be adjusted based on the detail design of the aircraft to comply with regulation requirements.

§25.1533   Additional operating limitations.
(a) Additional operating limitations must be established as follows:
(1) The maximum takeoff weights must be established as the weights at
  which compliance is shown with the applicable provisions of this part
  (including the takeoff climb provisions of §25.121(a) through (c), for
  altitudes and ambient temperatures).

MTOW affects many other aspects of an aircraft's performance. It will affect stopping distance after a rejected takeoff, takeoff performance (including engine failure), climb performance, taxi weights, and many structural aspects. MTOW will be chosen so that the requirements for all of these conditions are met. This is why new engines or winglets which improve performance will allow a higher MTOW.
Of course, as always, the pilot has the authority to set their own personal MTOW more conservatively, if they feel it is necessary for safer operation of the aircraft.

MTOW is defined and then verified by the manufacturer.
During "verification", tests and other analyses are conducted to show compliance to all MTOW related requirements. For example, landing gear analyses and tests are conducted for their corresponding FAR23 or FAR25 regulations. Flight Loads analyses/tests are also conducted, so that the structure can withstand all foreseeable loads during the entire operational life of the aircraft.
During the development of the aircraft, the MTOW can be updated (which is painful and costly) and during flight tests, final tuning can be required. Inceasing MTOW is more costly, in terms of development efforts and re-engineering of the aircraft. Decreasing MTOW would probably limit the operational capacity of the aircraft(less fuel, or less payload).

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Qualification Requirement of Aircraft taxi and landing lights?
Can anyone provide any standard through which taxi and landing lights are certified for use on aircraft?
And which certification is required for military aircraft lighting systems?

What country are you asking about?

for Indian aircrafts

There is no mention of any lighting regulations in the DGCA schedules however you should take a look at PART VI - AIRWORTHINESS as it will depend a bit on if the aircraft is Indian made or foreign built. From my reading of it if the aircraft is Indian built there is no regulation covering it but if the aircraft is foreign built, in order to receive and airworthy certificate you will need to cary over the foreign airworthy info. This may in turn mean that the light must adhere to the regulations of the certifying body of the aircraft such that the airworthiness can be carried over.  The actual usage of the light does not seem to be regulated under DGCA regulations.


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How do windshear warning systems work?
How do commercial aircraft windshear alert  warning systems work?

Do you mean Wind Shear? If you do, ATC may warn you of it if they are aware of it.

Modern commercial airliners have 2 different wind shear protection system:
1) predictive wind shear warning system
2) reactive wind shear warning system.
These systems work independently. PWS (predictive wind shear) works with weather radar. Reactive wind shear works with FAC ( Flight augmentation computer)
Basicly PWS can be switched ON and OFF from the WX-Radar  panel and it has some prerequisite for working :
Ground speed should be above 30 KTS, WX-Radar should be ON, At least one engine working etc. (may differ with different types).
PWS scans 5 NM ahead from 0-2300 ft and 1500 ft below according to phase of the flight. It works like a doppler radar. It scans the movement of air mass in front of you and "predicts" something goes wrong and warns you according to how bad is the situation. Doppler frequency will shift significantly in case of a microburst so PWS will catch this shift and warn pilots with amber or red cautions.
Reactive Wind shear system works with on board computers that takes real time data from all sources. This system will be active generally from 50 ft 1300 ft. (may differ)
Reactive Wind Shear basiclly monitors aircrafts energy level. For Airbus; FAC is responsible for that.
In computing the energy level FACs use different data from different sources: ADIRS - air, ground speed, vertical speed , slope. from other sources - wind gradient, vertical wind etc.
It will be active when the a/c energy level goes below predetermined threshold. It will alter from amber to red if your energy losing trend is faster.
You can read this document from airbus includes many general aviation information for more details :
http://www.airbus.com/fileadmin/media_gallery/files/safety_library_items/AirbusSafetyLib_-FLT_OPS-ADV_WX-SEQ02.pdf
Hope it helps.

Wind shear warning systems essentially augment the pitot-static system with a radar altimeter and/or GPS. The system bounces radar waves off the ground beneath it to get a true AGL altitude. The system also knows the topology of the region if it's given a GPS fix (GPS can also indicate AGL altitude but it's less precise than a radar altimeter). The warning will sound when the radar altimeter indicates a change in descent rate that isn't matched by the pitot-static system (the VSI will either indicate no change or it will be erratic, as the plane is essentially flying straight and level through a downward-moving mass of air), and not accounted for by known ground elevation changes. This same system can also warn of any dangerous descent rate (descending below a threshold altitude with gear up, at too high a speed, at too great a rate for landing, etc).

Wind shear is not always associated with a downward air mass.  It can also be a simple reversal of direction, or a marked change in speed at a particular level.  In this case, this system does not help.  Of course, the ASI will warn an attentive pilot and more modern weather RADARs use Doppler effects to measure and warn of wind shear.

@Simon - I don't disagree, but the most dangerous form of wind shear to an aircraft is a downdraft, for the simple reason that it pushes the aircraft toward the ground. A severe "downburst" is doubly dangerous because not only is the downward wind speed extremely strong, they usually happen in instrument conditions so visual cues that the aircraft is sinking too fast are sparse.


text:
Is the ILS CAT III system the most complex landing system available?
Is the ILS CAT III the most technologically sophisticated navigation / landing  system available for helping commercial pilots land a commercial passenger aircraft in severe and extremely low visibility weather conditions. Does the airport require special compatible equipment for this system to work properly?

Please clarify what you mean by "auto landing".  No aircraft can land fully automatically since, brakes, spoilers, flaps and gear cannot be operated by the auto pilot.

@Simon, I beg to differ, the autopilot I helped design and has been tested in flight 3 weeks ago, can :P

Your question is a little unclear (what does "sophisticated" mean?) but there are many questions on this site about autoland, ILS and so on. I suggest you review them first and then edit your question to be more precise. This one might be a good start, then this one.

@FLIGHTWARS the spoilers and auto brakes must be manually armed.  They are not armed by the autopilot (although Federico has built one that does).

@simon Well, the autopilot has to be setup for the approach and landing too, so arming those systems isn't really much different, especially since the question asks about the auto land system, and not the auto pilot...

Yes ILS equipment for CATIII is the most sophisticated across ILS systems. As people mentioned in comments there are another types of landing systems, which could be more complex.
No it is not auto landing system.
It self CATIII is a category of a landing conditions.
Also take a look here What is different between a Cat IIIA, Cat IIIB, and Cat IIIC ILS approach?

ILS creates a straight path for landing. Autoland is a mechanism that follows this path, including managing the flare. Cat III ILS are certified for a better precision and accuracy (as well as protection from interference). However MLS and GPS (GNSS) are far more complex.

Thx for links! Edit my answer.

The question asks if it is the most sophisticated landing system available, not if it is the most sophisticated ILS. :)

ILS Category 3C is true 'autoland' with no limitation regarding Decision Height for landing or Runway Visual Range. It's not especially complex (the equipment is not technically challenging)but has specific requirements regarding the equipment fitment for Cat 3C.
MWLS/MLS (microwave landing system) was researched which had some advantages including lifting the need to approach in a straight line. Although truly more complex than ILS, ther advantages it offered were not considered sufficiently worthwhile to proceed.
https://en.wikipedia.org/wiki/Microwave_landing_system
Today, the most complex 'landing system' is probably those based on GPS(GNSS). Several (smaller) countries have announced their intention to replace ILS provision with precision GPS or LPV approaches. This requires greater accuracy than unaugmented GPS can provide and this is achieved using Differential GPS and Wide Area Augmentation System.
https://en.wikipedia.org/wiki/Differential_GPS
https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System
The result is the LPV approach.
https://en.wikipedia.org/wiki/Localizer_performance_with_vertical_guidance
This is currently the most complex 'autoland' from a technical standpoint but still has DH/DA and RVR limitations, thus making it less 'complete' than ILS Cat 3C. It does not meet the ICAO Annex 10 precision approach standard.
Also see RNP, RNAV, LNAV, VNAV, PA, NPA, APV


text:
How does the lift-to-drag ratio depend on absolute sizes?
A dependency is provided here
$$(L/D)_{\max} = \frac{1}{2} \sqrt{\frac{\pi \varepsilon ~ \mathrm{AR}}{C_{D,0}}}$$
AR significantly affects the outcome in this dependency. AR varies significantly among different aircraft. AR doesn't depend on the overall absolute size.
Does $\varepsilon$ or $C_{D,0}$ depend on absolute sizes? Is there a size threshold beyond which $\varepsilon$ or $C_{D,0}$ becomes bad?
The Reynolds number is approximately proportional to the sizes and velocity. For small sizes, it's easier to achieve laminar flow without turbulence. At first glance, a smaller chord seems to be better than a larger one. Is there possibly a limitation on the maximum value of the velocity-chord product?
However, the opposite is claimed in this answer to the similar question Is there a maximum lift to drag ratio? . There suggesting that increasing a span is necessary rather than reducing a chord. Is there probably an optimal range for a chord size?
This question is about the interaction of surfaces with air. This question is not about wing strength. This question is not about wing deformation under its own weight.

Does $\varepsilon$ or $C_{D,0}$ depend on absolute sizes?

$\epsilon$ is in the range 0 to 1 and mainly depends on the spanwise lift distribution, so it does not directly depend on the global size of the airplane. Values >0.8 are common. $C_{D,0}$ does depend on the size of the airplane since it represents its global aerodynamic drag (except the drag due to lift which is captured by the other terms in that equation).

The Reynolds number is approximately proportional to the sizes and velocity

Reynolds number is not "approximately" proportional to speed and size rather it is directly proportional to them being defined as:
$Re=\frac{\rho Vc}{\mu}$
where $V$ is the speed and $c$ the length of the body.

For small sizes, it's easier to achieve laminar flow without turbulence. At first glance, a smaller chord seems to be better than a larger one.

Not really. Laminar flow doesn't always imply less drag. The ubiquitous plot of the drag of a sphere versus Reynolds shows that quite vividly (plot source):

At higher Reynolds number the boundary layer becomes turbulent and that actually helps the airflow stay attached to the body and globally reduces drag. This is in general true also for an airfoil with the added benefit of obtaining a delayed stall i.e. more lift at higher AoA.

However, the opposite is claimed in this answer... suggesting that increasing a span is necessary rather than reducing a chord.

That answer states (correctly) that increasing the span (i.e. the aspect ratio) is a good way to reduce the (induced) drag. It also states that if this increase is done maintaining the wing surface constant then it brings a reduction in the chord and therefore in the Reynolds number with the consequences just said before about the sphere.

The Reynolds number is not directly but is approximately proportional to velocity. Because reynolds number depends on viscosity and density. Viscosity depends on temperature and pressure. Density, temperature, pressure of gas depend on velocity, because gas undergoes compression near the wing.

@Imyaf: yes and know. When those plots are traced, they always consider the freestream condition, i.e. the fluid far from the aerodynamic body. Otherwise the Reynolds number (or the Mach number or any other number) would change according to which precise point on the stream you are considering and that would make things simply impossible to be compared.


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Lift Coefficient question

I am making a RC Airplane, it has a wing profile as shown above. What might be the approx. lift coefficient of this? The wingspan is 80cm, what will the lift provided be by this wing at 65kmph ?

At which angle of attack? If it's at 0 deg (the way you drew it), the first part will push the wing down. For a flat plate we have some answers here; like this one

During take-off it will be at around 15-20 degrees AOA, how will the behavior be then?

at that angle of attack the lift coefficient will be about 0.8, the average value for separated flow.

And what if I increase the angle between the two parts to 170 deg?

I'd expect it to work better the other way around, i.e. with the profile flying to the right of your picture.
140° is way too low, the airflow will almost certainly detach by that corner. Values >170° should be considered. I'd start with 185° and then decrease it in small steps.
A relatively high pitch nose-down should be also expected.
Maybe you can replace the kink with a more or less continuous curvature plus a fully bent nose section to get something like the "KFm-5b" in this picture.

Oh, if I go ahead and increase the angle to about 170 degrees, using it in the same orientation as I posted, would there be a higher lift at around 10degrees AOA ?

Also, at 170 degrees, would it be more efficient than a flate plate? Also, I cannot get rid of the kink since I am using a very stiff foam, so is there any workaround or can you please suggest a better airfoil without smoothened edges?

If you use the same orientation as posted I fear you'll get more drag than lift. To be conservative I'd reverse the orientation, limit the short part to 10% of the chord and use 170° as angle between the two parts. A small bumb on the upper surface by the leading edge would also help with the transition of the boundary layer to turbulent. Afterwards you can play around with the geometry, but I'd use that one as basis.

I have a propulsion system which is a propeller which I believe can counteract the drag. please correct me if I am wrong. So what would the lift coefficient at my orientation, 170 degrees 10 deg AOA be ?

As @PeterKämpf already said, no more than 0.8

Oh, 0.8 is perfect! thanks

But why not a simpler flat plate then? Less drag, less pitching moment and less vibrations...

I just wanted to experiment with different simple wing shapes


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Aircraft operation management
I found this in the USITC website "In 2020, air freight experienced two different, but related impacts associated with the COVID-19 pandemic. The first, and most significant, impact was a sharp decrease in capacity to transport freight in the cargo holds of passenger aircraft (“belly cargo”) due to cancelled flights." https://www.usitc.gov/research_and_analysis/tradeshifts/2020/special_topic.html#:~:text=In%202020%2C%20air%20freight%20experienced,%E2%80%9D)%20due%20to%20cancelled%20flights.
What is the reason for this?

Think about it. If that was enough, then the incremental cost for passengers - a little more fuel, salary of flight attendants, would be far less than the incremental revenue for passengers and the airline industry would be a lot more profitable than it currently is.

Think about the cost of a human plane ticket vs sending a package.

Cargo airlines are profitable otherwise they simply wouldn't exist. But if you can use only half of the airplane (i.e. only the belly) then it might get ineffective.

It depends. Profitability doesn't depend on the quantity of load (cargo/passengers) but on how much you get paid for that. COVID was also beginning of supply chain crisis, so sender where happy (sometime) to pay much more for quick delivery. Also consider many planes were grounded (so less supply), so it was an adjustment of demand and supply. Do no look only on one minor part.

It requires a complex business analysis that is actually not trivial at all, which is why i can't answer. You would need detailed cost and revenue data to calculate a break even point, which will vary widely by aircraft type, leg length, etc. There are a lot of variables to consider! Who do you need to convince, and what do you need to convince them of?

Compare passenger and cargo revenue and costs between Q1 2019 and Q1 2021 (source with other interesting figures and analyses)

@mins, thanks a lot for the reference!

It’s worth remembering that many cargo routes are very unbalanced, so your belly cargo must to able to pay for both legs of the trip (or close to that).

@jcaron great point! Thanks a lot!

In normal operations it is carefully balanced.
Longhaul passenger planes normally carry some freight - and this adds up to quite a capacity. If these flights are cancelled - the freight capacity drops significantly.
And the number of freighters is limited - so they can not take over all the drop in capacity.
And yes, it is possible to fly the passenger planes with only cargo - but this is not nearly as cost efficient as both passenger+freight or freighters alone. In that time it has also been tried to "seat" freight in normal passenger-seats - but this is by far not as efficient as loading normal freight.

Thanks a lot. I can image that flying only cargo is inefficient. However, inefficiency is more general than "profit-losing". Mu puzzle is that we know that cargo demand is very high during COVID. If flying an passenger aircraft with only cargo goods is profitable (but inefficient), why belly capacity dropped so much during COVID?


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Communication between Tower and Plane seeing a UFO
I am looking at pilot-to-tower communication and I'm coming up empty: can someone give me a brief set of dialog based on this non-correct communication?
This is for a piece of fiction (happening in the United States). I'm looking for three or four short sentences between the airplane and tower when the plane's pilot is seeing a large, impossible looking object at some distance and is asking the tower (?) if they "see it as well"?
Plane (747 Major Air-line): Tower are you picking up anything [ location ~70 north of the airport ]?
Tower: No, Flight[number], what are you seeing?
Plane: "Some kind of atmospheric phenomena?" [inaudible]
Tower: Say again?
Plane: There appears to be some kind of extremely large object at 35000 feet. It appears to be a dark colored pyramid. I can't tell if it's real or--
--Tower receives priority information from FAA (or more appropriate government office)--
Tower: We're not seeing-- wait. Please emergency divert [ to?? ]. We have a serious condition and need to clear all air corridors (?).
Plane: "It's heading directly at us, Tower. We are diverting."
---END
If this is inappropriate for this forum, I'm sorry--I did look up a lot of pilot-to-tower jargon and I couldn't find even basic stuff that works for it. If someone can give me a quick run through of what jargon might be used, I'd be very thankful.

If I'm understanding right, you're writing a piece of fiction and you're asking to make this (inherently unrealistic) dialogue sound more realistic? Phraseology will heavily depend on whether the interaction is happening in the United States or some country that is not the United States, and it will depend to a lesser extent on which specific the non-USA country it is.

This may well be better suited to Worldbuilding.

Sorry, but the alternative to "sounds about right" is pretty much "please rewrite the dialogue", and that isn't really on-topic for this forum.

Tower does not control airspace 70 miles away at 35k'.

Yes, it's for fiction. I was trying to get some kind of realistic tower-to-airplane dialog as a preface. I get it's a strange and probably off topic request. This just seemed like the place that I might be able find answers. The country would be the USA. Modern day.
If re-writing the dialog is off topic, perhaps the solution would be some pointers to what might happen if  a plane sees something that seems impossible and wants to know if someone else is seeing it too?

I'm no expert on any of this, but I think some of the concern here is the use of "Tower" - "Tower" means an airport, and an airport won't be controlling space 70 miles away. Air Traffic Control in general does, but (again, not an expert), while a pilot at 35,000 feet can see well past 70 miles in clear skies, I doubt they would be able to reasonably judge distances beyond a few miles - i.e., they'd know there is something in a particular direction that is either big and far away or HUGE and not as far away.

If the plane is at cruising altitude, it would not communicate with tower, but a center.
Initial contact would be for example: "Denver Center, Delta 123".
ATC would then reply "Delta 123 go ahead".
Then the exchange could go as you described, up until the point where the ATC commands the plane to turn, which would be something like this:
"Delta 123 turn immediately heading 180!" (or suitable compass heading for your scenario).
Delta would reply "heading 180 for Delta 123"
Center might give extra info after Delta reads back the turn instruction.

The suitable radio callsign for the center in your scenarion location can be found here: https://en.m.wikipedia.org/wiki/Area_control_center

Thank you! I did look for this stuff. I wasn't able to get very far. I greatly appreciate the help there.

@MarcoChacon Some background info: Center is looking at a radar screen. "Primary radar", meaning the classic "send a pulse and look for a reflection", tends to be spotty and somewhat inaccurate, especially for small planes. Most aircraft have a powered transponder (also called "secondary radar") that transmits a numeric code back when the primary radar set triggers it, making that plane show up clearly and distinctly. Fancy transponder can also transmit precise altitude and airspeed information.

@Jpe61 why don't you post your answer as an answer and not a comment?

It's certainly reasonable for center to see a large object without a transponder under primary-only and be unsure of what they're detecting, but I'm not sure how they'd go from "I don't see anything" to "immediate turn heading xyz". An object larger than an airliner would be very clear almost regardless of composition unless it had stealth characteristics, but if it did then it would probably have to actively do something to ruin the stealth effect for it to suddenly show up (a physical change to the shape, like when a B-2 lowers the gear, or turning off shields, or whatever).

@U_flow at the time I made the comment the question was closed, there was no way to answer it.

@Jpe61 you can do it now. I think your comment contains all information OP is looking for

@U_flow done, thanks for the heads up

The scenario you describe sounds a lot like the Japan Air Lines Cargo Flight 1628 incident. You can read a transcript of the ATC communications.

If the plane is at cruising altitude, it would not communicate with tower, but a center. Initial contact would be for example:
"Denver Center, Delta 123".
ATC would then reply:
"Delta 123 go ahead".
Then the exchange could proceed as you described, since unusual communication such as the one you described does not have a standard phraseology to follow, up until the point where the ATC commands the plane to turn, which would be something like this:
"Delta 123 turn immediately heading one eight zero!" (or suitable compass heading for your scenario).
ATC might stress the urgency of the command by continuing:
"I Say again Turn immediately heading one eight zero! (note that headings, flight levels and most numbers in general are read out in single digit numbers)
Delta would reply:
"heading 180 for Delta 123" Center might give extra info after Delta reads back the turn instruction.
The suitable radio callsign for the center in your scenarion location can be found here: en.wikipedia.org/wiki/Area_control_center

A small point: Why would ATC command a turn to 180°, they don't see anything on their screen (which should be a SSR, so without transponder nothing will be visible). In case of accident after the turn., ATC unmotivated request may be criticized. I believe the crew should ask a clearance for a turn if they think this is what to do.

I assumed they received information necessitating the turn to some direction, since the question reads: Tower receives priority information from FAA (or more appropriate government office)

I stand corrected, makes perfect sense.

There was some discussion in the comments about primary radar. In high-altitude airspace all aircraft are required to have a transponder which transmits an active reply when pinged by ATC radar systems, and controllers who are working that kind of airspace exclusively are not required to display primary-only radar returns on their scopes. So the "additional information" the controller get could be them turning on primaries and seeing something there.
Note however that primary radar (at least the kind used by ATC) only shows a target's 2D position over the ground. It does not indicate how high the target is. Military primary-only radar might be designed to also scan for vertical information but an airliner at cruise would not be talking to a military controller.
With that said, and remembering that this is a very unrealistic scenario, here is a slightly more realistic exchange:

Pilot: Center, you got any traffic for Delta 123? Five miles or so?
ATC: Delta 123, negative, no traffic in your vicinity... I can check primaries.
Pilot: Yeah Center, I'm seeing something right in front of us, dark pyramid or something, same altitude.
ATC: Traffic alert, Delta 123, twelve o'clock, three miles, altitude unknown. Advise you turn right heading one-eight-zero immediately.
Pilot: Right one-eight-zero, Delta 123.

This scenario wouldn't necessarily cause the pilot to request a diversion, but if for some reason you want ATC to initiate the diversion it might be something like this:

ATC: Delta 123 we need to get all traffic down immediately. You're cleared to the Denver airport via direct, descend and maintain flight level two-three-zero.

Your scenario is rather similar to this scene from Close Encounters of the Third Kind which is lauded as being very accurate to ATC phraseology, equipment, and working environment. It's a little bit dated now but it still sounds extremely realistic. Note how the Ares pilot initiated evasive maneuvers on their own rather than waiting for an ATC clearance, once they determined that there was a danger to the aircraft.


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Is Fluid Structure Interaction considered in aircraft design?
Fluid Structure Interaction (FSI) causes an  aeroplane’s geometry to change and hence the forces on the different surfaces of an aeroplane become different than the forces expected according to initial calculation.

Is this Fluid Structure Interaction considered while calculating
forces (and hence the final design) of aircraft while finalizing
the designs for aircraft?
If it is considered, what are the available software packages which could be used to analyse this?

Another common term is aero-elasticity.

Aero-elasticity is a very vague term, and you can consider FSI to be a subset of aero-elasticity. but the particular problem where you find iteratively the effects of aerodynamic forces on structure, and then find the forces on the deformed structure is FSI

Terms are as vague your definitions of them. I don't think as FSI as a subset of aero elasticity, quite the opposite. FSI deals with all kinds of fluids and structures, e.g. hydraulic lines, pumps, cardiovascular mechanics. Aero-elasticity is a subset of FSI, it only deals with the interaction between flow of air and non-rigid structures.

deflections must be considered, if relevant in the force (pressure) distributions and if relevant for the aerodynamic and structural design of the aircraft. In addition to that, flutter, buffeting and other fluid-structure (aeroelasticity) effects must be considered as well. In addition to that, when relevant, aero-servo-elasticity (the dynamic behavior of the aero-structure AND the response of the control system to that behavior) is also considered. This becomes a critical analysis for some designs (like, high aspect ratio or highly flexible aircraft), and has historical stories (good, funny or bad consequences).
For static aeroelasticity, you can go iteratively by hand or by using simple calculations. But especially for dynamic cases, if you do not go into simplified approaches, it generally requires Nastran or other off-the-shelf of home-developed FSI capable solvers.

This page has a picture showing the relationship between flight related phenomena: http://www3.imperial.ac.uk/aeroelastics/projects/flexibleaircraft
(aeroelasticity , flight mechanics, flexible body dynamics)

Just one example: Good designers put the aileron pushrods away from the elastic axis of the wing to enable the deformation of the wing to create a damping deflection of the ailerons. This is especially helpful for high aspect ratio wings:

When the wing flexes, the pushrod will not be compressed, so will become relatively longer than the surrounding wing structure. This will create a negative aileron deflection which works against the lift force which flexes the wing in the first place. Doing this is particularly helpful in damping wing flutter.
Generally, the engineers make sure that every aircraft component works as intended even when the structure is deformed. Another example: To compensate for differences in the thermal expansion of different components, pushrods in glass fiber fuselages have two halves, connected by a pivoting lever, so that changes in their length will compensate.

Aero-elasticity is indeed considered in design and certification of aircraft.
One software package that I know is capable of aero-elasticity computations is NASTRAN / PATRAN. No doubt there will be others.

After consulting with some seniors, I've come to know that Ansys workbench (Which effectively uses NASTRAN on the backend) has the proper tools for achieving this using combination of FEM and CFD


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Regular procedure followed by the pilots before takeoff?
What are the list of procedures (checks) followed by A320 and A380? Are these procedures decided by the airlines and (or) the manufacturer, or by the Civil Aviation Regulatory Authority of the respective country?

The checklists are prepared by the manufacturers and the airlines. But the details will be very different depending on the type of aircraft so it isn't really possible to give a single checklist, unless it's a very generic one. Can you explain a bit more about exactly what information you need?

Which checklist are you asking about? E.g. the before takeoff checklist? It will differ between different aircraft models, so specifying only the A320 or only the A380 will also help.

I've already editted the question specifically for A320 and A380, why the "On Hold" then?

Because it's still incredibly broad.  Every airline will have it's own check lists for aircraft operation, and those checklists (when compiled together) usually are hundreds of pages long.  You'd be better off asking for a specific checklist, for a specific operation for a single airliner...

Though, you also might consider taking that second question (about who makes the checklists) and making it it's own question.  It's a great question, I'd like to see the answer myself.

@JayCarr Done..! http://aviation.stackexchange.com/questions/15671/who-decides-the-regular-procedure-followed-by-the-pilots-before-takeoff

Nice!  Upvoted it, hoping for an answer :).

You can find online Flight Crew Training Manuals which contain instructions about what to do at different stages of the flight. Checklists are part of this preparation and verification. FCTM for A320. PPRuNe has the answer you may look for.

This is three completely separate questions, two of which have essentially one answer per airline that operates the plane. That's ridiculously broad.

Try to search "Before Takeoff Checklist". Manufacturer will provide standard checklist but airlines can modify it.

this is more a comment than an answer


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How does a wing mounted jet engine on a supersonic airplane prevent the interference in the flow due to Shock?
Wing mounted jet engines face the free stream at Mach number 1 or above, and they work perfectly for Mach numbers below 1 as well, even though the free stream characteristics change a lot after Mach 1.

How do the engines manage to work despite the fact that after Mach 1, the Shock waves would try and disrupt the normal airflow?
If the engines are optimized to work at above Mach 1, does this cause any trouble for them to work under subsonic conditions?

Don't confuse with "Why cant jet engines work with supersonic flow?"

you cannot simply add a line like that: Don't confuse with "Why cant jet engines work with supersonic flow?" why? what makes this question different?

Which aircraft which has wing-mounted engines and is capable of supersonic flight do you have in mind? Because I can't think of any (assuming you mean hung in pods below and ahead of wings and not stuck to underside like Concorde or B-1B, which look very different)!

The answers to the linked question do actually answer this question.

Flow conditions are not so different, only the reaction of the flow to an obstacle is. By shaping the intake appropriately, supersonic flow is handled easily, and shocks will be helpful in decelerating and compressing the flow.
However, supersonic flow demands sharp intake lips which are hit by the flow at the right angle, otherwise drag rises quickly to intolerable levels. These sharp lips will cause flow separation in subsonic flow when hit by the flow at an angle, so aerodynamic tricks like bypass doors need to be added to the intake to keep flow angles at the intake lips in check.
Note that the intake will ensure a flow speed around Mach 0.5 at the compressor face of the engine, regardless of flight speed. Therefore, the engine will not need to be optimized for supersonic flight. However, to keep its frontal area low and the nozzle speed high, its bypass ratio should be low. The only troubles this causes are increased engine fuel consumption and noise.

" ... its bypass ratio should be low".  A-ha. Watching an old video about B-58 Hustler development I think, it mentioned offhandedly that some design consideration allowed to the bypass ratio to be kept low. I thought that odd, now I see.


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How much time it will take a B787 to fuel completely when empty?
When a big jet like B787 needs to be fueled with empty tanks, ideally how much time it will take to go full?

According to Boeing (via airliners.net), it takes 53 minutes to load 55,800 US gallons with two fuel trucks operating at 35 psi delivery pressure. The total fuel capacity of the 787-8 is 33,340 US gal, so fueling from empty to full should take about 31.6 minutes with two trucks.

That's a fantastic answer, but may I trouble you for a source?

@Lightsider here is the source : http://www.airliners.net/aviation-forums/tech_ops/read.main/335483/

55800 US gallons is about 200 tons. How do you get that into 2 fuel trucks?

@steveverrill most large airports have hydrant system which feed fuel to trucks. The truck just pump the fuel from hydrant to plane.


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Do commercial airliners have the tail number placed somewhere on a placard in the cockpit?
I notice, looking at pictures of various light singles, that the tail number of the aircraft is typically prominently displayed somewhere towards the top of the instrument panel. If it were your own plane, you would quickly memorize it given the dozens of times per flight you have to give your callsign, but it's still useful for new pilots, rentals and trainers.
That led me to wonder: are the tail numbers of commercial aircrafts also posted in the cockpit, or is it omitted because commercial airliners more often use their company and flight number as their callsign, while the equipment used for a flight can change every time? I don't see any registration number label in this shot of a 737 cockpit, for instance, but it could be on the overhead panel obscured in this shot.

If there is a Selcal receiver, its code shares a placard with the registration number: B777, B737, A340.

Some modern airliners have an electronic display for the flight number as well (updated before each flight naturally). For instance, in this picture of the A380 cockpit, DLH363 (Lufthansa flight #463) appears in the top right of the two lower FMC displays.

@ZachLipton: DLH363 is not a "tail number".

True. My point was that the question mentioned how company and flight number are normally used as callsigns for commercial flights, so I thought it was useful to point out that airliners are starting to include an "electronic placard" for this information. It's not an answer so I didn't post it as one.

Yes. The tail numbers are indeed places on a placard inside the cockpits of commercial airplanes. Following are some examples:

Yes, on a commercial airliner typically the tail number and the SELCAL (if so equipped) are placarded on the panel.  It's hard to find sometimes in picture because it may be behind the yoke, but it should be there somewhere.


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What system populates the Flight Stats?
Which system is in place which gets data from all the flights on a terminal and display them every where like Airport Screens, Websites, different Apps etc?

The TV screens in a terminal are called Flight information display system.

The same system which populates all the data on displays in a Railway Terminal.
For a standalone airport, this data can be mined from ATC of that airport (Which has all the data regarding incoming/outbound flights ).
On an International scale, the data has to be mined from various different agencies. According to a data provider FlightStats:
It gets data from:

Complete, accurate data is the cornerstone of our business and what
sets us apart from competitive solutions:
Geographic Coverage - FlightStats provides definitive information for approximately 99.5% of U.S. flights, and better than 86% of
flights worldwide.
Completeness - FlightStats queries multiple sources to create a record for each flight enabling us to offer a broader range of
information (for example, gate information).
Accuracy - We have invested heavily in the areas of parsing, interpretation and error checking and developed the logic that enables
handling of difficult issues such as cancellations, diversions and
changing schedules.
Codeshare Support - Our codeshare logic enables us to deliver flight information for both the operating and the marketing carriers,
filling what is often a major gap in coverage.
Real-time data sources include:
FAA ASDI Data Feed
European Data Feed
GDS (Sabre, Amadeus, Apollo, Galileo)
Direct Airport / Airline Data Feeds

Batch data sources include:
Innovata Schedules
TSA Security Wait Times
Security Information
Health Information
Consular Information

For the system which gets all this data from various different sources, its the central computer database of the airport, which gets data from ATC and the a fore mentioned sources, and this database is accessed by many other end users, including the Screens in the airport


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What does it mean when the controller uses the word "request"?
I recently had the opportunity to fly a PAR approach into Büchel Airbase in Germany. It was a ton of fun and I'll definitely try it again when I get the chance. However, as we were getting set up for the approach I received the following call

(callsign) request heading

It caught me off guard, and it took a while but I eventually interpreted it as "say heading" and gave him my current heading. He didn't complain, but I'm still not sure if that's what he wanted.
A bit later I got a similar call

(callsign) request QNE

However, I was unfamiliar with that Q-code1 and only later found out it means "pressure altitude". Q-codes suck. Anyway I said "Say again" and he came back and asked how many were on board (which I incorrectly assumed at that point was what QNE meant), again, using "request".
Anyway, I've never heard a controller say "request" before, is it just army version of "say"? I'm pretty sure the guy was German, so it might be a German military thing, or a NATO thing, or just a simple mistake on his side?

1: As a private pilot in Europe, you pretty much need to know QNH, QFE, QDM and QTE

Congrats on the first question on Aviation!

@GarrisonNeely; Thanks, I love the platform, been waiting for this one to enter beta for quite some time. :)

In civil aviation the ICAO standard phraseology should be used. This phraseology is described in ICAO document 9432.
According to the definition in Doc 9432, Chapter 2, section 6, the word request means: "I should like to know ..." or "I wish to obtain ...".
It is used for example by pilots to ask for a clearance to climb to an altitude (e.g. request flight level 360).
The standard ICAO phraseology is to use the word report in the first example in your question.
According to the definition in Doc 9432, it means: "Pass me the following information ..."

[callsign] report heading

The second phrase quoted in your question is even stranger. QNE is the standard pressure altimetry setting of 1013.25 Hectopascal (29.92 inches of mercury in the US). When an altimeter is set to standard pressure, the normal way of reporting the altitude is in Flight Levels. So in this case the standard phraseology should have been

[callsign] report Flight Level.

Could you cite where you pulled the ICAO standard phraseology from? Generally, "report" is used when they would like you to notify them upon reaching a certain location or altitude, and "say" is used when they'd like you to inform them of something current... at least in the US.

@BretCopeland see edit. To be exact: ICAO DOC9432, Chapter 2, section 6: Standard words and phrases. ATC in the US uses a lot of non-standard phraseology, which unfortunately frequently causes confusion to international pilots.

Just a note on a common misunderstanding: QNE is actually indicated altitude when 1013 is set. Unlike ONH and QFE it is not the pressure to be set into Kollsman's window, but the "indicated pressure level" (still a pressure mind you) at your aircraft's location. QNE for example will change when your aircraft climbs/decends. QNH and QFE will not

@Radu094; "indicated altitude when 1013 is set", that would be pressure altitude, no? Oh, I see, @DeltaLima said it was the setting, not the altitude (I said altitude in the question), although he went on to say it refers to altitude in flight levels. So yeah, maybe a bit of clarification is not wrong :)

@Radu094, do you have any official document to back that up? As far as I know QNE is the standard altimeter setting, not pressure altitude itself.

@roe, when the altimeter is set to 1013.25 the altitude that is indicated is referred to as pressure altitude and communicated in Flight Levels. When someone asks your QNE, of course he means your indicated altitude when the altimeter is set to 1013.25.

definition of QNE and another one apparently it's (pressure altitude at) field elevation..?

Ouch. So QNE refers to pressure altitude, but measured at rwy threshold not on the airplane!! Boy, I'd say 99% of textbooks on aviation need to have their pictures corrected.

"Request " is very common in Europe but it's usually the pilot who will use it to talk to ATC, as in "Request taxi" or "Request to enter your airspace".
I've never heard this phrase being used by a controller in Belgium, France and The Netherlands (where I've flown the most so far). Seems very odd to me.

Right, of course I use request all the time, never had anyone say it to me though. Any experience with military controllers?

The few times I've spoken to military controllers they didn't request something. They ordered me to do or say something :-). On a serious note, it could very well be something specific to military airspace though.

In the U.S., I think the controllers would typically use the phrase "callsign, say heading" rather than the verb "request".  Pilots would usually be the one to say "request", but I don't think there's anything technically wrong if controllers use it.  You clearly understood the intention.

@bovine; actually, during the first second or so, I thought he'd just asked me to request a heading, which I couldn't wrap my head around, so I wouldn't say i understood it clearly. :) Funny how the mind works sometimes when it's faced with the unexpected.


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Can a Boeing 767-200 fly at 510 knots at a height of 400 metres?
Can a Boeing 767-200 physically fly at 510 knots at around 400 metres altitude?
If it did manage that speed, how likely would a structure failure be?
Also, if those measurements were achieved, how difficult - relatively - would it be to control?

What do you mean by relatively?
Also, when the maximum indicated cruise speed of this plane is below 500 knots at cruise altitude, why would you ask such a question?

Thank you Vivian. By 'relatively' I mean how difficult would it be to control at 400m at that speed compared to cruising altitude? Reason for the question is I am looking into something that stated those measurements for that aircraft.

I hope you understand that this question is ALSO an Engine related question, rather than only being the air-plane related question?

Yes, true. Therefore I would extend my question to query whether the engines can produced enough thrust for the increased drag at that altitude etc. Please ignore my ignorance as I am not a pilot or engineer and do not have extensive knowledge - hence my question...

You may want to add the constraints that the aircraft must be in horizontal flight, without wind. And you should replace height (AGL) by altitude (AMSL) if this is what you mean

It sounds like you're asking if 9/11 was faked.

@VictorJuliet The cruise speed of a Boeing 767 is not below 500 knots true airspeed during cruise. It is below 500 knots indicated airspeed.

The speed is secondary - what determines the physical limits of the Boeing 767 is Mach number and dynamic pressure.
510 kts at 400 m in standard atmospheric conditions equals Mach 0.775. This is well within the limits of the Boeing 767. But at 400 m it produces a dynamic pressure of 40,567 N/m², and that is too much. The maximum dive speed $v_D$ of the 767 is 420 kts.
This only means that flying at 510 kts is illegal, but it is still possible. If the airplane dove down to those 400m from enough altitude, it would entirely be capable to reach this speed, but would slow down once it stops diving.
There are several effects which can cause a catastrophic failure when flying too fast:

When the aircraft flies into a gust, the resulting load factor can overstress the structure.
When the pilot commands large control inputs, he will also overstress the structure.
Flutter might also cause structural damage.

The maximum Mach number of the 767 is 0.91 (0.05 above the maximum cruise Mach number, which is 0.86), and this corresponds to 523 kts in 11,000 m.  Thankfully, certification requirements demand a margin of 20% between the maximum speeds and flutter onset speeds, so flutter might be close, but is still tens of miles per hour away when diving to 510 kts. Remember, to experience flutter you need also to excite the motion first. Here is a good discussion of this topic.
In short, flying a Boeing 767 in 400 m at 510 kts is not recommended, but is entirely possible and most likely even safe when done in calm air and by a calm pilot. It only won't last long, because the engines will not produce enough thrust to maintain that speed. Flying this dive requires guts, but no special skills.

There’s also the issue of Vmo vs Mmo.  The Vmo is 360 KIAS vs 602 KIAS corresponding to an Mmo of 0.91 at those altitudes.  Presumably Boeing engineers in a buffer of 20% or so prior to the onset of control surface flutter, so that would allow for a maximum forward speed of 430-440 KIAS prior to the onset of control surface flutter.  I don’t think you could get to Mmo at low altitudes like that.

@CarloFelicione Flutter depends on TAS. v$_{MO}$ is not the limit, that is v$_D$. You need to apply the flutter margin on top of maximum TAS and v$_D$ will give you the maximum dynamic pressure.

It would, in all likelihood, be impossible for a large transport category jet to even reach an airspeed of 500 knots at an altitude that low. Drag increases with the square of the airspeed and the transsonic region presents some additional challenges on top of that.
A 767 should have sufficient thrust to accelerate past Vmo at low altitude, but Vmo for a 76- is 360 knots at MSL, a long way away from 500. Even if structural and powerplant failures due to overstress weren't an issue, it's safe to say that a 76- would be drag-limited from reaching anywhere near 500 knots in level flight.
With respect to failure modes, there are structural concerns, skin integrity concerns, powerplant concerns, and Mach tuck, and one or more of these would be encountered long before you had a chance to read 500 on the Airspeed Indicator.

Bending of the airframe - going sufficiently fast will induce the various aerodynamic structures on the aircraft the generate forces and turning moments in excess of what the structure was designed to handle, leading to plastic deformation (and possibly outright failure if the stresses are sufficiently large)
Control surface flutter - this is probably less of a concern in fly-by-wire and hydraulically-actuated control surfaces than for free control surfaces, but at sufficiently high speeds, air particles will strike the control surfaces with sufficient force to displace them and cause them flutter (ailerons are by far the most susceptible to this and the infamous control column "buzz" is caused by this). Sufficiently aggravated flutter has caused control surface separation in several fatal accidents.
Skin integrity - sufficient suction over the top of the wings has been known to cause material, rivets, and inspection panels to separate and compromise the surface. Probably less of a concern for a stressed aluminium metal or composite skin than for a canvas skin.
Mach tuck - the center of pressure moves rearward along the wing chord when the aircraft enters the transsonic regime (the exact speed and characteristics of this shift differ by aircraft) and causes nose-down pitching moments, which may become impossible to overcome. This effect is aggravated in a conventional tailplane arrangement by the generation of standing shockwaves and the subsequent change in airflow separation characteristics.
Powerplant failure - reaching 500 knots would require the powerplant to generate tremendous amounts of thrust, requiring a much greater displacement of air through the compressors (and turbines) and a much hotter burn in the combustion chamber. The resulting engine rotational speeds and temperatures would ruin the engine for further use, if not cause it experience an outright structural failure. There's a pretty infamous case of an Egyptian MiG-25 overflying the Sinai Peninsula at Mach 3+ (the Foxbat was rated for a maximum of 2.8); the engines were toast afterwards.

Though not necessarily a failure mode, something to watch out for in fast-travelling swept-wing aircraft with large wingspans is the possibility the aerodynamic forces might twist the wingtips to the point where aileron functionality is reversed from normal.
Lastly, the control difficulties at such a high speed would stem more from the fact that the control surfaces (especially ailerons) become much more effective at higher speeds (less displacement is necessary in order to generate the forces necessary). Ordinarily, this might lead to an aircraft that is responsive bordering on twitchy and would require very light control inputs, but the story is a bit more complicated in an aircraft like the 76- due to the role played by the envelope protection software and the hydraulic actuation system.

Keep in mind that the speed of sound decreases with temperature (and thus altitude), This means that at low altitude 510 knots will be a lower Mach number, than the same speed at a high altitude.
510 knots is approximately Mach 0.76 at low altitude

@ROIMaison - Absolutely, but the critical Mach number of a subsonic wing can be well below the local speed of sound, even for a swept wing aircraft.

@habu - brilliant answer thank you very much - just what I was looking for (though I will have to go off and research some of your "techy" terminology!)

Does 767 have envelope protection? As far as I know, 777 is the first Boeing plane with FBW, not 767. Of course flight envelope protection would not let the plane exceed Vne.

@JanHudec - Some envelope protection would be present, especially in the form of stall protection, overspeed annunciators and the like, etc., but I was thinking more in terms of adjustments to control surface actuation rate as a function of airspeed - and I have no idea if the 76- features anything like it.

@cloudnine - you can always ask what terminology you're unclear on and folks here will be happy to explain. there are a few other threads on here dealing with high speed flight in case you want to learn more.

@habu: I don't count annunciator as envelope protection. By "flight envelope protection" I mean something that will not allow pilots leave the flight envelope at all. And I believe anything like that only exists on A320+ and B777+, but not B767.

@habu: But critical Mach number will be the same at any altitude and speed at which Mach tuck will cause problems will be $M_{NE}$ or above. And $M_{MO} = 0.86$, so $M_{NE}$ is more than that (something like 0.92, but I can't find reference now).

@JanHudec - fair point about Mach tuck not likely being an issue in this particular scenario; I included it in the list for the sake of completeness with respect to the issues surrounding high-speed flight in subsonic aircraft.


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How to calculate the wing chord of the aircraft Aero A.10?
Can anyone explain how to find the wing chord of the aircraft Aero A.10? Given Wing Span = 46.6 ft and Wing Area = 549 sqft. Thanks

Can anyone please calculate for me. uhm, no? we can teach you how to do it, but this website is not for solving your homework.

Okay, so can you please teach me howto calculate for the wing chord of this certain aircraft? Thanks Federico

I'm voting to close this question as off-topic because "please do my homework for me".

@VictorJuliet:  This is why we don't answer homework questions:  It just encouraged the poster to ask another question again, without putting forward any effort towards answering the question himself.

In the previous question he asked (which was closed of course because of its low quality), someone suggested him to post this as a seperate question, as this made more sense. Have a look at the comments on this: http://aviation.stackexchange.com/questions/16823/from-the-chosen-aircraft-calculate-the-lift-drag-tail-load-and-forward-inerti

how to calculate [...] the wing chord?

Given the data you provided you can only compute the SMC (Standard Mean Chord), that is equal to:
$$SMC = \frac{S}{b}$$
where $S$ is the wing surface and $b$ is the wingspan.

Given the information in your question, it has to be assumed that the wing has a rectangular planform (because you mention no sweep angle and taper ratio). For a rectangular planform,

span * chord = area
chord = area/span = 11.78ft

Thank you so much. Wonder why people are so mean :( I just need help thats all :(

No Mark, you aren't asking for "help".  You're asking for the answer.   "Help" is when you start with "Here's what I tried, the formula I used, why it didn't work, and why I'm stuck".  That makes for a complete effort and a good question.  You didn't do any of that.


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Can carrier-based aircraft takeoff while the carrier is stationary?
Reading about aircraft carrier operation turns out that carrier operation relies a lot on catapult and carrier itself turns into wind with high rev on propellers. This generate as high wind speed as possible to make a takeoff easier for fixed wing aircraft.
My question is in the absense of carrier's own speed and turning into the wind, would fixed-wing carrier-based aircraft be able to takeoff using catapult and its power alone?

If they don't carry a full load of ordnance and fuel, why not? Adjust the minimum speed appropriately by reducing take-off mass, and you can take off with the catapult, but without headwind.

If the carrier can't turn into the wind, this certainly depends entirely on the wind speed and direction.

Perhaps the carrier will at the very least need to maneuver to face into the wind. I can't see a fighter landing or taking off in a crosswind very easily (relatively narrow wheel separation on main landing gear).

This was covered at length in Tom Clancy's Debt of Honor.  Also, carrier aircraft can always do as strategic bombers and spy planes do: launch on bingo fuel, and immediately hit the tanker.

Aircraft carriers using STOBAR (the skyramp) always need to maintain a speed of about 55kmph in order for the aircraft on them to take off. This is done to generate enough windspeed on the deck to assist the aircraft to take off. And STOBAR system already hampers the carrying capacity of aircraft, so for takeoff from a STOBAR carrier at rest, a further reduction in takeoff weight of the aircraft would be required to generate enough lift for the aircraft to take off at such low speeds. This reduction in weight would depend on the aircraft carrier and the aircraft as such and might create scenarios where this is entirely not possible.
For Aircraft Carriers equipped with CATOBAR, the conventional steam piston drive which is used to catapult the aircraft provides approximately 95 MegaJoules of energy to accelerate the aircraft to speeds where it can takeoff safely. Hence the arguments stated about the STOBAR carriers can be sequentially applied to this class as well. But recent Electromagnetic Aircraft Launch System provides around 122 MegaJoules of energy to accelerate the aircraft. Given the extra amount of energy available to accelerate the aircraft at higher speeds, it is quite possible that it is going to be easier for the aircraft to take off from a static aircraft carrier equipped with electromagnetic catapults when compared to the aircraft carriers equipped with convention steam piston catapults. But the exact details for the feasibility of this idea would be a matter of national interest and might not be available online.
Also, one should not ignore the extra amount of stresses that an aircraft would have to face while taking off from a stationary aircraft carrier as it would have to accelerate to a higher speed at the same available length of the runway and hence this might prove detrimental to the lifetime of the aircraft.
Edit:
Under research technologies such as Ground Carriers, if implemented would also assist further in reducing the weight of the aircraft and hence make it easier for the aircraft to take off from carriers at much lower speeds.

Given the extra amount of energy available to accelerate the aircraft at higher speeds, it is quite possible that it is going to be easier for the Aircraft to take off from a static aircraft carrier equipped with electromagnetic catapults  -- Pilots (and equipment) don't like sudden changes in velocity that much. I'm pretty sure it will be possible, but SOP will probably still be steaming into the wind to reduce the acceleration required to reach a flying airspeed.

"Aircraft carriers using STOBAR (the skyramp) always need to maintain a speed of about 55kmph in order for the Aircrafts on them to take off." That doesn't seem to be true. The British Invincible class carriers had a maximum speed of around 52kph and used STOVL. That would leave the carrier unable to launch aircraft if it couldn't reach its maximum speed.

@DavidRicherby I think Victor's statement refers primarily to conventional aircraft using the "ski jump"; The Russian Navy launches Su-33s this way, and the Indian Navy has a few skyramp launchers for the HAL Tejas. When using STOVL aircraft and a skyramp like the Sea Harriers aboard the Invincible, you don't need as much airspeed because you're using thrust for lift. Those Harriers could, in an emergency, do a pure vertical takeoff, but that uses a lot more fuel and has a lighter MTOW so they prefer the ramp (which works for a Harrier even when the carrier is at idle).

Carrier takeoffs depend on three factors to establish aircraft airspeed. Wind velocity (means speed and direction), aircraft speed, and ship speed. That is why most carriers are travelling into the wind at 35 mph or more. If a catapult developed 150 mph speed, and the wind speed is 10 mph, and the ship is heading into the wind at 10 mph, an aircraft with a 170 mph go/ no go threshold would be pushing the envelope. This is why most carriers like a 20 to 30 knot bow wind over the deck. It makes take offs possible and landings far easier.
In theory, a 20 knot wind properly aligned and 150 mph catapult could launch some fixed wing aircraft.

USS Saratoga launched all aircraft that it could while sitting in Athens harbor August 15, 1971. The first day in port, I was on night shift the night before and my buddy came to wake me up and when I got up I noticed the ship was pitched enough that I was walking uphill. A huge salt water hose broke (about 36inches maybe bigger) and they launched A/C to get weight off the ship. We were about 1 mile from the shoreline. A F-4 pilot made his last carrier takeoff that day as he barreled rolled at a couple hundred feet above the beach at the shoreline.

Cool story! I assume the got the leak stopped & water pumped out okay? Welcome to Av.SE!

So why was that the the pilot's last carrier takeoff?  Because he broke regulations by doing the barrel roll and got demoted?  Because he was leaving anyway and figured he might as well show off?  Or because his barrel roll ended in the water?


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What are the vertical pieces of metal on the Slingsby Swallow wing for?
I was watching James May's Toy Stories, particularly the one where they try to fly a glider across the English Channel.  In the middle of the episode they mention a glider that was used for training in the RAF during the 1950s.  It was called the Slingsby Swallow, and it looks like this:

When I saw those pieces of metal coming out of the wings I was...surprised.  At first I thought they were split flaps but then I found another picture and became even more confused:

The devices are clearly coming out of the top and bottom of the wing, not the trailing edge.
Does anyone know what these are and what they are used for on the Slingsby Swallow (or any other aircraft the employs a similar device)?  My only guess is that they are some sort of spoiler that may reduce lift to help get the glider on the ground...but I'm uncertain.

@FreeMan I just wish he'd make more!  There are only, like, 10 as far as I can tell.

TheTvDB lists 12 episodes from Dec '05 - Dec '14. 6 "Regular Series" episodes, and 6 "Special" episodes. +eleventy on making more!  But... we're wandering waaaaay off topic...

Just a clarification because it is not mentioned explicitly in the answers: every single glider built in the last 70 years has them.

You're correct -- they're speedbrakes, often referred to as spoilers, and are retracted when striving for efficient flight, but are generally extended in the landing pattern so that you have correction available if you start to get slightly low.  Also frequently extended when the glider is left on the ground to reduce the effect of gusty winds & the likelihood that they would lift a wing.

Should that read "generally retracted in the landing pattern..."? That way you can extend them to help slow down if needed. I'm not a glider pilot so I might be wrong here :-)

@aviationstats I'm not a pilot of any kind, but I think the post is correct -- if you plan to land with them extended, but get low, you can retract them to return to the planned flight profile.

@aviationstats Not a typo in my answer -- "generally extended in the landing pattern" is what I meant to post.  In a glider, you have various ways of getting rid of energy (extend downwind, use spoilers, sideslip), but no way to create it.  So you plan your pattern to start at "this" point & "this" altitude, fly with partial or full spoilers, turn base "here," and everything will work out.  Then, if you find you're a bit low, you retract the spoilers until you determine that you're back on path.

To clarify, I agree with @RalphJ but I was taught to normally not use the spoilers on final turns, etc as you can lose height very rapidly! (OK in exceptional cases though.) Ideally a perfectly judged circuit would be finishing final turn in a position to use half spoiler for the final approach - you can then use less or more as necessary. It's also OK to use them anytime on downwind or base leg if high in the circuit.

@RalphJ Interesting analogy is when sailing through a crowded mooring field with lots of anchored boats I was always taught to aim a course at the stern of a moored boat. The boats point into the wind & a sailboat has several ways to fall away from the wind but it's much harder to sail closer upwind. If you try to pass an anchored boat close to the bow of an anchored boat & have to adjust course it can get very hard to adjust course upwind.

If you observe the image below, in the marked areas, you'll see a rectangular patch (it's very faint):
These are the places over and below the wing where the "Devices" you mentioned are housed. These devices are called Dive Brakes. They are used as spoilers to increase the drag while flying so as to lose altitude by increasing the drag (and hence the name). These can be retracted when not required, and deployed when required. The patches in the image are the housings where these are actually deployed from and retracted back to.
And from Ralph J's answer, they can be left deployed when the plane is on ground, as its a very light plane and gusts and winds can actually cause the plane to lift if enough drag is not there.

I don't think I've ever heard them being called “dive brakes” on anything else than a dive bomber. They are called “spoilers” or “air brakes”. The later is more general term; “spoilers” extend from the upper wing surface, “air brakes” may extend on other places as well. And note that most “dive brakes” actually are not “spoilers”, because “spoilers” spoil lift and a dive bomber is going to need a lot of lift to pull out of the dive.

I researched a bit and the wiki article clearly states this. :(

Interesting to note the Slingsby Swallow's wikipedia page does use the term "Dive brakes". I've never heard that term used on any glider, though if Slingsby used that name there may be documentary evidence... Note "Spoiler" and "Airbrake" tend to be used casually by pilots regardless of the actual effect of the device. Properly, spoilers don't reduce speed much but disturb airflow (especially above the wing) and reduce lift, increasing the descent angle. They are used for pinpoint landings, not speed limiting. True spoilers might not reduce speed very much in a near vertical dive...

Nice high-viz color scheme--

Re the "dive brakes" thing, my glider club insructors (USA) teach a memorized pre-flight checklist that goes A, B, B, C, C, C, D.  Guess what "D" is for?  Granted it's generally more common to hear pilots refer to the surfaces as "airbrakes" or "spoilers", but a word starting with "D" makes for an easier-to-remember checklist sequence...

When I saw those pieces of metal coming out of the wings I
was...surprised.

I don't think anyone has pointed out yet that those spoilers/airbrakes/dive brakes are constructed mostly of out wood, not metal.  As is the rest of the Slingsby Swallow.
Some gliders (e.g. Schweizer 2-22/ 2-33/ 1-26) use a different style of spoiler/airbrake where the surface is hinged on its leading edge, and lays down flat in a slight recess on the wing when not in use, rather than rising vertically up out of a deep "well" or slot in the wing.